COMPARATIVE STRUCTURE OF THE VISUAL-SYSTEM OF LYNX SPIDERS (OXYOPIDAE) AND ITS RELATION TO HABITAT AND BEHAVIOR

Lynx spiders (Oxyopidae) are known to be hunters living in low herbace ous vegetation or bushes. Observations of their sexual and predatory b ehaviour suggest that visual stimuli are important. The arrangement of eyes is characteristic of the family Oxyopidae, but the eye structure of oxyopids is poorly known. The microanatomy of adult eyes in Peucet ia cauca, P. gerhardi and P. graminea, and in Oxyopes lineatus was com pared. Generic and specific differences were detected in the ocular ar eas and relative dimensions of the lens, as well as in the other compo nents of the eyes. The dioptric apparatus and photosensitive segments of retinal cells in all eyes are larger in O. lineatus than in Peuceti a species. Differences between species were also observed in the exten t of retinal pigmentation: processes of pigment cells surround the rha bdoms up to 85% of their height in O. lineatus, but to only 60% in Peu cetia species. Calculations from histological measurements of inter-re ceptor angles and F-numbers provide an approximate idea of the perform ance of the visual system. Anterior-lateral eyes of O. lineatus may ha ve the best resolution power, while the small anterior-median eyes, wh ich are very similar in all species, seem able to form bright but not well-resolved images. Posterior eyes, together with AL eyes, which exh ibit a rudimentary tapetum, appear to have a good ability to perceive movement. Comparison is made with lycosid and ctenid eyes the secondar y eyes of which have a thick grid tapetum. The functional significance of the observed differences in eye structure between Oxyopes and Penc etia species is discussed in relation to levels of illumination in the microhabitat utilized and to predatory and reproductive behaviour.